Figure 3. Effect of pH on AMAC labelling of polysaccharides treated with or without ^•OH.

Citrus pectin, homogalacturonan, tamarind xyloglucan and wheat arabinoxylan were pre-treated with NaBH₄, which reduced any oxo groups already present, then incubated with (+) or without (−) an ^•OH-generating Fenton system (ascorbate + Cu²⁺ + H₂O₂) and finally washed by ethanol precipitation. The polysaccharides were then labelled with AMAC at pH 2.0–7.0. Unreacted AMAC was removed by ethanol washing and the polysaccharides were analysed by TLC. Fluorescence at the origin indicates polysaccharide labelling.